Bonga is the first deepwater project for the Shell Nigeria Exploration and Production Company (SNEPCO) and for Nigeria. The discovery well is located in oil prospecting license (OPL) 212, which was awarded during Nigeria’s first round of deepwater frontier acreage awards in 1993.

SNEPCO operates the field on behalf of the Nigerian National Petroleum Corporation (NNPC) under a production sharing contract, in partnership with Esso (20%), Nigeria Agip (12.5%) and Elf Petroleum Nigeria Limited (12.5%).

Crude oil production from the field started in November 2005 and the first shipment from the field was made in February 2006. Production was stopped temporarily due to a militant attack in June 2008 and was resumed later in the same month.

Bonga exploration

Bonga lies 120km southwest of the Niger Delta, in a water depth of over 1,000m.

The real extent of the Bonga field is some 60km². After acquiring and processing 3D seismic data in 1993 / 94, the first Bonga discovery well was drilled between September 1995 and January 1996. Recoverable reserves are estimated at 600 million barrels of oil.

“Recoverable reserves are estimated at 600 million barrels.”

In May 2001, Shell drilled an exploration well on Bonga Southwest located some 10km southwest of the Bonga field. Bonga Southwest was drilled in a water depth of 1,245m.

The well reached its final depth of 4,160m and was subsequently logged and suspended. It encountered a substantial amount of net oil sand.

An initial evaluation of the well results indicated that the recoverable reserves discovered with Bonga Southwest were large enough to form the basis for a new deepwater development in OML118.

FPSO

Shell decided on an FPSO development solution. The field has around 16 subsea oil producing and water injection wells tied to the FPSO. AMEC secured the £300m ($463m) offshore contract for the engineering design, fabrication, integration and commissioning of the 17,000t topside production facilities in 2001. These were necessary to produce around 200,000 barrels of oil and 150 million standard cubic feet of natural gas a day.

The newly built hull arrived in the UK during the third quarter of 2002, following its construction in the Far East under a separate contract. The topsides were installed onto the hull to create the 300,000t FPSO.

Bonga contracts

ABB won the $180m order for the engineering, procurement and construction (EPC) of all of the subsea equipment. This also included production-control umbilicals and gas-lift risers.

“Bonga lies 120km southwest of the Niger Delta.”

As part of the contract, ABB supplied 29 conventional subsea trees and associated hardware to facilitate oil production from and water injection into the reservoir. Equipment delivery continued until mid-2009. The workscope encompassed project management, engineering and the supply of manifolds, trees, wellheads, controls, connection systems, intervention equipment, integration testing and installation support.

Stolt Offshore signed an agreement for a turnkey subsea construction contract. Valued at about $200m, this contract covered design engineering, procurement, installation and commissioning of the gas-export pipeline, production flowlines, water-injection lines and steel catenary risers.

Stolt Offshore began design engineering and procurement work immediately. The risers were fabricated in the second half of 2002 at the Stolt Offshore Nigerdock pipe reeling facility, in Nigeria.

The installation workscope included rigid steel flowlines, together with steel catenary oil and gas-production risers. Seaway Polaris installed 36km of 10in-diameter production flowlines and all the project’s steel catenary risers using the J Lay method.

Additionally, Seaway Polaris handled the installation of the 92km-long, 16in-diameter gas-export pipeline from the Bonga FPSO, to the Shell EA riser platform. Seaway Kestrel installed 25km of 12in-diameter water-injection flowlines. Survey and tie-in work was undertaken by Seaway Legend.

ClampOn delivered a topside system of sand sensors in February 2003.

An extension to the field, Bonga Northwest field, is situated in OML 118. It lies at a water depth in the range of 2,953ft to 3,937ft. This field will be developed by 12 subsea wells tied back to Bonga’s FPSO.

Gas and oil export

“ABB won the $180m order for the EPC of all the subsea equipment.”

Gas from the Bonga is piped to the Nigeria Liquefied Natural Gas (NLNG) plant at Bonny, where a third processing train was constructed. LNG is exported to Atlantic and European markets via tankers. Prior to direct offloading, the oil will be stored on-board the production facilities.